Phosvitin (PSV) is considered as a good emulsifier, although it has a low proportion of hydrophobic regions and steric hindrance. Wheat gluten (WG) possesses excellent hydrophobicity and macromolecular network structure. In this work, WG was subjected to a series of Na 2 SO 3 solution, followed by cross-linking with PSV under transglutaminase (TGase) catalyzation. The results showed that Na 2 SO 3 could break disulfide bonds of WG and increase its solubility from 7.33% to 42.82% with 1200 mg/L of Na 2 SO 3 . Correspondingly, the cross-linking degree was significantly enhanced. Compared to PSV, the cross-linked PSV-WG exhibited a higher surface hydrophobicity and thermal stability, with a lower zeta potential and apparent viscosity. The emulsifying activity of PSV-WG reached 17.42, 20.63 and 20.28 m 2 /g with Na 2 SO 3 concentration of 300, 600 and 900 mg/L, which were all higher than that of PSV (15.19 m 2 /g). This work provided a novel strategy to elevate emulsifying properties of PSV by cross-link reaction.
Mei An,Xiaoxiang Cheng,Xinsheng Luo,Tao Yang,Xianpeng Sun,Jingtao Xu,Dao Xiao,Daoji Wu,Heng Liang
Ultrafiltration (UF) is a highly efficient technique for algal-rich water purification, but it is heavily contaminated due to the complex water characteristics. To solve this problem, potassium permanganate (KMnO 4 ) oxidation enhanced with sodium sulfite (Na 2 SO 3 ) was proposed as a pretreatment means. The results showed that the end-normalized flux was elevated from 0.10 to 0.91, and the reversible fouling resistance was reduced by 99.95%. The membrane fouling mechanism also changed obviously, without the generation of cake filtration. Regarding the properties of algal-rich water, the zeta potential was decreased from −29.50 to −5.87 mV after KMnO 4 /Na 2 SO 3 pretreatment, suggesting that the electrostatic repulsion was significantly reduced. Meanwhile, the fluorescent components in algal-rich water were significantly eliminated, and the removal of dissolved organic carbon was increased to 67.46%. In the KMnO 4 /Na 2 SO 3 process, reactive manganese species (i.e., Mn(V), Mn(III) and MnO 2 ) and reactive oxygen species (i.e., SO 4 •− and • OH) played major roles in purifying algal-rich water. Specifically, SO 4 •− , • OH, Mn(V) and Mn(III) could effectively oxidize algal pollutants. Simultaneously, the in-situ adsorption and coagulation of MnO 2 could accelerate the formation of flocs by decreasing the electrostatic repulsion between cells, and protect the algal cells from being excessive oxidized. Overall, the KMnO 4 /Na 2 SO 3 process showed significant potential for membrane fouling alleviation in purifying algal-rich water.
A rapid method based on extractive electrospray ionization mass spectrometry (EESI-MS) has been developed for quantitative detection of trace radioactive molecular iodine-129 (129I2) in negative ion detection mode in ambient air. For actual air samples, gaseous 129I2 was completely converted into iodine-129 ions (129I−) by an excess of Na2SO3 solution. By adding excess amounts of 127I2 into the solution, the 129I− ions formed triiodide ion complexes (i.e.129+127*2I3−) which were subjected to tandem mass spectrometry experiments to exclude false positives. Quantification of iodine-129 was achieved by quantitatively measuring the characteristic fragment (i.e., 129I−) of the triiodide ion complexes. The calibration curve showed a good linearity within an relatively wide concentration range of 0.01–1000 ppb (R2 = 0.991), a limit of detection (LOD) of 4.5 ppt and a relative standard deviation (RSD) of 4.0–13.1% (n = 5). The spiking recovery of this method was found to be 82.6–110.5%. The method had also been successfully applied to detecting the trace amount of gaseous 129I2 released in a simulated nuclear leakage accident, showing a satisfactory result for the tested gaseous samples. The experimental data demonstrated that EESI-MS was a useful tool for quantitative measurement of radioactive iodine in cases such as nuclear leakage, nuclear explosions and related scenarios.
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